in egypt, prosecutors began to make their case in the trial of former president hosni mubarak. they accused him of tyranny and corruption during his decades of rule, in the first of three days of opening statements. mubarak could face the death penalty if convicted. his two sons and eight other defendants also are on trial. those are some of the day's major stories. now, back to judy. >> woodruff: and we return to today's official kickoff of the 2012 presidential campaign. jeffrey brown takes a wider historical view. >> brown: and for that, i'm joined by presidential historians michael beschloss and richard norton smith, scholar in residence at george mason university. and with us from iowa tonight: jeff stein, vice chair of the board of trustees for the state historical society of iowa. michael, i want to pick up on something that judy and gwen reminded us of. there's a democratic caucus tonight. there's an incumbent president, a democrat. what is the incumbent normally what happens with the incumbent? they normally stay out of the action or fight for relevancy? >> well, proba